Heat-recoverable article

ABSTRACT

An article comprising a heat-recoverable conduit is provided with a plug or cap within or around said conduit to prevent the ingress of contaminants. The plug or cap comprises two principal parts; the first part, which is hollow, sits inside or around the conduit and the second part, which is attached to or in engagement with the first part, blocks the conduit. The second part can be detached or disengaged before recovery so that, for example, a supply line can be passed through the conduit and the first part can then be removed, destroyed or deformed prior to or during recovery. The plug or cap may also act to prevent premature recovery of the conduit.

This application is a continuation of application Ser. No. 071,535 filedJuly 9, 1987, now abandoned, which is a continuation of application Ser.No. 06/845658 filed March 26, 1986 and now abandoned, which is adivisional of application Ser. No. 06/079335 filed September 22, 1979and now U.S. Pat. No. 4,579,148, which is a continuation of applicationSer. No. 06/846322 filed October 28, 1977 and now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to heat-recoverable articles and methods fortheir use.

Heat-recoverable articles, especially heat-shrinkable articles, are nowwidely used in many areas where insulation, sealing and encapsulationare required. Usually these articles recover, on heating, towards anoriginal shape from which they have been previously deformed, but theterm "heat-recoverable" as used herein also includes an article which,on heating, adopts a new configuration, even if it has not beenpreviously deformed.

Heat-recoverable articles are typically made from polymeric materialsexhibiting the property of plastic or elastic memory as described, forexample, in U.S. Pat. No. 2,027,962 and 3,086,243. In other articles, asdescribed, for example, in British Pat. No. 1,440,524, an elastomericmember such as an outer tubular member is held in a stretched state by asecond member, such as an inner tubular member, which, upon heating,weakens and thus allows the elastomeric member to recover. Finally, ithas more recently been found that heat-recoverable articles can also bemade from certain metal alloys. Such alloys, sometimes called "memorymetals", are described for example in U.S. Pat. No. 3,174,851 and3,351,463, and the book "Shape Memory Effects in Alloys" Jeff Perkins,Plenum Press, New York and London, 1975.

In many applications, especially those related to the installation andrepair of supply lines such as electricity cables and gas pipes, theheat-recoverable articles are exposed to contaminants such as insects,moisture, gas leaks etc. which may damage or interfere with thefunctioning of the articles themselves and/or associated equipment. Ingeneral the material of the heat-recoverable article and its designensure that the contaminants are excluded after recovery but problemsmay arise during storage and transport of the articles and/or inapplications, such as the wall feedthrough device described and claimedin British Pat. No. 1,245,119, where the heat-recoverable article may beinstalled on site some time before recovery is effected.

In yet other applications, it may be desirable to effect recovery of oneportion of a heat-recoverable article whilst avoiding premature recoveryof another portion. Amongst such articles there may be mentioned, forexample, distribution caps for junction boxes in cable televisionsystems such as CATV (Consumer Antenna Television). These distributioncaps have a plurality of heat-shrinkable conduits each adapted toreceive and, on heating, grip, a cable passing into the junction box.The number of cables passing into a given box may vary from area to areaor from time to time, with the result that it may not be necessary toemploy all of the conduits or that it may be desirable to employ some ofthe conduits during a first operation and others in a second, lateroperation. A serious problem arises, however, in that the necessaryclose proximity of the conduits makes it difficult, if not impossible,selectively to recover some of the conduits by heating withoutsimultaneously at least partially shrinking the others.

Another article of this sort is a telephone exchange distribution box. Amulticore cable comprising many individual wires is lead into such abox, the unused wires being capped and remaining within the box whilstthe other wires are led out through conduits which are heat-recovered tohold the wires in place and to seal the box. Further heat-recoverableconduits are, of course, provided for future use of the capped wires.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an article having a heat-recoverableconduit therein, said conduit being provided with a plug or cap membercomprising

(a) a first hollow part which lies inside or outside a length of theconduit in contact with the wall thereof, and

(b) a second part which blocks the conduit, the second part being soattached to or so in engagement with the first part that it can at leastpartially be detached or disengaged so as to leave the conduit open withthe first hollow part still in position inside or outside the conduitbut removable or deformable so that recovery can be effected.

DETAILED DESCRIPTION OF THE INVENTION

An important characteristic of the present invention is that the secondpart, which ensures the effective closure of the conduit, can beremoved, still prior to recovery, so as to allow a substrate such as asupply line to be properly positioned within the conduit, beforerecovery is effected, whilst the first hollow part remains in position.Thus even if, as in many preferred applications, the conduit is providedwith an internal lining of a hot-melt adhesive which may have becomebonded to the first hollow part during partial recovery, to secure theplug or cap in position, the supply line can be located within theconduit without the worry of the premature recovery which might, forexample, be caused by the heating necessary to soften the adhesive toremove a solid one-part closure such as a bung.

In certain applications it may be desirable for the plug or cap to bemade from such a material that, and/or be so designed that, when inposition inside or outside the conduit it prevents or at least impedesrecovery thereof.

Accordingly, in one aspect the present invention further provides amethod of differentially recovering heat-recoverable conduits in asituation in which the heat required to recover one conduit mightotherwise cause at least partial recovery of another conduit, whichcomprises blocking a conduit which is not required to recover with aplug or cap member as defined above whilst applying the heat necessaryto cause the desired recovery of the other conduit or conduits.

In general, such conduits will be parts of a single article such as atelephone exchange distribution box or the two ends of an open tubularsleeve as described above and, in another aspect, the present inventionprovides a heat-recoverable article comprising a plurality ofheat-recoverable conduits, one or more, but not all, of which is/areblocked with a plug or cap member as defined above.

Although, in certain applications, some or all of the conduits may beheat-expansible, they will, in most cases, be heat-shrinkable and, forconvenience, the present invention will, from now on, be described withreference to heat-shrinkable conduits. In such cases, the plug memberwill in general be positioned within the conduit. However, in certaincases a cap member may be employed, part of which is positionedexternally of the conduit, and which prevents recovery of the conduit byshielding it against heat applied to recover the other conduit(s).

The second part of the plug or cap acts to close the conduit against theingress of moisture and other contaminants. In certain preferredembodiments it also acts to retain the first part in position inside oroutside the conduit. That is to say, whilst the second part remainsattached to said first part it is difficult to remove the plug or capfrom the conduit. When, however, the second part is detached from thefirst part or is otherwise displaced before use of the conduit, thefirst part can itself relatively easily be removed or deformed. Onesimple manner in which this can be achieved is to form the second partwith a flange which sits on a lip of the conduit and prevents movementof the plug or cap out from the conduit. Other means, for example screwthreading, may also be employed.

The second part may be attached to the first part by, for example, aline of weakness so that it may be torn away from or knocked off thefirst part. However, other means may be employed to ensure that thesecond part is detachable from the first part or can otherwise bedisplaced. In this respect, it will be appreciated that, in manyapplications, it will be sufficient only partially to detach the secondpart from the first part so as to open the conduit prior to recovery.

The first part of the plug or cap member is preferably shaped orotherwise formed so as to facilitate its removal from the conduit whenthe second part has been detached or disengaged. In an especiallyadvantageous embodiment, the surface of the hollow part in contact withthe conduit, e.g. the outer surface of a generally cylindrical plugmember, is slightly tapered, e.g. at an angle of from 1° to 10°, so thatit "milks out" from the conduit when heat is applied to the latter tocause it to recover, the initial radial recovery forces of the conduitco-operating with the taper to cause the part to be expelled from theconduit in the direction of the longitudinal axis thereof.

In another embodiment, the first part may, for example, be formed as ascrew-threaded part which is unscrewed from the conduit prior torecovery. (In this and other embodiments it may be advantageouspartially to pre-shrink the conduit so that it firmly retains the plug.)

In certain embodiments of the present invention, the plug or cap memberis advantageously made from a rigid but relatively fragile material,such as bakelite, so that it may be removed by breakage once it hasfulfilled its function. It may additionally be advantageous to providethe plug or cap member with one or more lines of weakness, e.g.longitudinal grooves, to facilitate its breakage and removal.

In a further embodiment of the present invention, the first hollow partof the plug or cap member may be formed from a helically wound length ofmetal or plastics wire or strip, which can be removed simply by pullingone end to cause it to unwind.

In yet other embodiments the first hollow part may be so constructedthat, and/or may be made from such a material that it need not beremoved prior to or during recovery. For example, where differentialrecovery is required, the first part may be made from a material, such ahot-melt adhesive, which has a melting or softening temperature suchthat it remains solid under the heat is experiences whilst other nearbyconduits are being recovered but deformed, e.g. melts, upon directapplication of heat to its own conduit. It will be appreciated that thefirst hollow part may also be constructed so as to be mechanicallydeformable the deforming force being either the recovery force or anexternally applied force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents the end of a distribution cap;

FIG. 2 is a side view taken along the line indicated by the arrow II inFIG. 1;

FIG. 3 is a section through a plug member;

FIG. 4 is a section through an outlet conduit in a distribution cap;

FIG. 5 illustrates the plug of FIG. 3 positioned inside the conduit ofFIG. 4 prior to recovery;

FIG. 6 illustrates the position after a cable has been passed throughthe conduit of FIG. 5, the plug member has been broken and removed andthe conduit has been heat-recovered;

FIG. 7 illustrates a second form of plug member positioned within aconduit;

FIG. 8 illustrates a third form of plug member positioned within aconduit;

FIG. 9 illustrates a fourth form of plug member positioned within aconduit;

FIG. 10 is a section through said plug member; and

FIGS. 11a-d represent the use of yet another form of plug member inaccordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIGS. 1 and 2 there is shown a distributor cap 1 provided with fourheat-recoverable outlet conduits a, b, c, and d. FIG. 4 shows one ofthese conduits in more detail, the expanded inner diameter s of theconduit typically being about 30 mm and the recovered inner diameter ttypically being about 15 mm. The inner surface of the conduit will, ingeneral, be lined with suitable hot melt adhesive.

FIG. 3 shows a plug member for use in accordance with the presentinvention in restraining recovery of the conduit of FIG. 4 whilst one ormore of the other conduits is being recovered. As shown, the plug member2 comprises a first part 3 which is adapted to be positioned within theconduit and which has an outer surface 4 which is tapered from one ofits ends to the other and a second part 5 which is adapted to close theconduit whilst the plug member 2 is in position. A line of weaknesscomprising an annular groove 6 joins the first part 3 and the secondpart 5. The dimensions shown will typically be as follows:

m=30 mm; n=22 mm; o=26 mm; p=30 mm; q=33 mm and r=36 mm. The slope ofthe outer surface 4 will typically be about 30%.

In FIG. 5 the plug member 2 is shown positioned within the conduit. Itcan be seen that the tapered surface 4 of the first part 3 combines withthe second part 5 effectively to prevent removal of the plug member 2from the conduit in either direction. If desired the conduit may bepartially preshrunk about part 3 of the plug member 2.

FIG. 6 shows the position after a cable 7 has been forced through theconduit breaking the second part 5 of the plug member 2 from the firstpart 3. Upon heat-recovery and shrinkage of the conduit the first part 3has then been forced out in the direction shown by the arrow III withthe result that the cable 7 is now securely gripped by and sealed withinthe conduit.

In the embodiment shown in FIG. 7 two fingers 8a and 8b retain the plugmember in position prior to recovery. When it is desired to effectrecovery, cap 9, which has a circular line of weakness 10, can beknocked out from a conduit by a cable and the fingers 8a and 8b can bemoved together whereupon the conduit may shrink, the part 11 "milkingout" as described above. If desired a further line of weakness 12 may beprovided so that the fingers 8a and 8b can be broken away from part 11prior to recovery.

In FIG. 8 yet another form of plug member is shown which comprises afirst part 13, having a tapered outer surface similar to that of theclosure 2 of FIG. 3, and a second part 14. A line of weakness comprisedby annular groove 15 separates the parts. As shown, in this embodimentthe conduit has been partially preshrunk about the plug member so as toform an inner shoulder 16 which co-operates with parts 13 and 14 toprevent removal of the plug member, the remaining part of the conduitbeing non-shrinkable. However, when a cable is forced into the outlet,part 14 is broken off in the direction shown by arrow IV, and uponheating, part 13 "milks out" in the direction shown by arrow V to allowfull recovery.

FIG. 9 shows yet another form of plug member in accordance with thepresent invention in which the second part 17 acts to block the conduitand is held in position by resilient fingers 18 and 19. This second partis attached to a tapered first part 20 via a line of weakness comprisedby circular groove 21 and can be removed by breaking at this line ofweakness when the resilient arms 14 and 15 are forced inwardly as shownby the arrows VI. The first part 20 then "milks out" as the conduitrecovers.

FIG. 10 shows how the first part 20 is provided with two diametricallyopposed grooves 22 and 23 so that it can readily be broken, for example,manually or with a pair of pliers, after recovery has taken place.

FIGS. 11a-d illustrate a different type of embodiment in accordance withthe present invention. In this embodiment a plug member 24 is made froma hot melt adhesive and is positioned within the outlet by partialshrinkage of the latter. When it is desired to effect full recovery thecap 25 of the plug member 24 is broken off from the recovery restrainingtubular part 26. Cable 27 is then positioned within the conduit and heatrecovery is effected, during the course of which tubular part 26 meltsand acts as a sealing adhesive.

Whilst the present invention has been particularly described withreference to distribution boxes, tubular sleeves and feed-throughdevices it will be appreciated that it may be used in any applicationwhere an article comprising one or more heat-recoverable conduits isemployed.

We claim:
 1. A method of differentially recovering heat-recoverableconduits, which comprises:(1) providing an article comprising aplurality of heat-recoverable conduits whose mutual proximity is suchthat heat required to recover one conduit might otherwise cause at leastpartial recovery of a proximate conduit; (2) inserting a plug memberinto said proximate conduit thereby blocking said proximate conduit,said plug member comprising:(a) a first hollow part which lies inside alength of said proximate conduit in contact with a wall thereof, and (b)a second part attached to the first part so that the second part can atleast be partially detached so as to leave the conduit open with thehollow first part still in position inside the conduit but removable sothat recovery of said proximate conduit can be effected, said firsthollow part in combination with said second part capable of blockingsaid proximate conduit; and (3) heating said one conduit while saidproximate conduit remains blocked.
 2. A method of differentiallyrecovering heatrecoverable conduits, which comprises:(1) providing anarticle comprising a plurality of heat-recoverable conduits whose mutualproximity is such that heat required to recover one conduit mightotherwise cause at least partial recovery of a proximate conduit; (2)placing a cap member on said proximate conduit, said cap membercomprising:(a) a first hollow part which lies outside a length of saidproximate conduit in contact with a wall thereof, and (b) a second partattached to said first part so that it can at least be partiallydetached so as to leave the conduit open with said first hollow partstill in position outside said conduit but removable therefrom so thatrecovery of said proximate conduit can be effected, said first hollowpart in combination with said second part blocking said proximateconduit; and (3) heating said one conduit while said proximate conduitremains blocked.
 3. A method of differentially recoveringheatrecoverable conduits, which comprises:(1) providing an articlecomprising a plurality of heat-recoverable conduits whose mutualproximity is such that heat required to recover one conduit mightotherwise cause at least partial recovery of a proximate conduit; (2)inserting a plug member into said proximate conduit, said plug membercomprising:(a) a first hollow part which lies inside a length of saidproximate conduit in contact with a wall thereof, and (b) a second partattached to said first part so that it can at least be partiallydetached so as to leave the conduit open with the first hollow partstill in a position inside the conduit but deformable so that recoveryof said proximate conduit can be effected, said first hollow part incombination with said second part blocking said proximate conduit; and(3) heating said one conduit while said proximate conduit remainsblocked.
 4. A method of differentially recovering heatrecoverableconduits, which comprises:(1) providing an article comprising aplurality of heat-recoverable conduits whose mutual proximity is suchthat heat required to recover one conduit might otherwise cause at leastpartial recovery of a proximate conduit; (2) placing a cap member onsaid proximate conduit, said cap member comprising:(a) a first hollowpart which lies outside a length of said proximate conduit in contactwith a wall thereof, and (b) a second part attached to the first part sothat it can at least partially be detached so as to leave the conduitopen with the first hollow part still in position outside the conduitbut deformable so that recovery of said proximate conduit can beeffected, said hollow first part in combination with said second partblocking said proximate conduit; and (3) heating said one conduit whilesaid proximate conduit remains blocked.